Security systems frequently employ combinations of video monitoring and/or motion detectors which sense intrusion into an area. The former requires real-time surveillance by an operator while the latter is subject to frequent false alarm conditions.
U.S. Pat. No. 5,586,063 to Hardin et al., which is assigned to the assignee of this application and is incorporated herein by reference, is directed to a passive optical speed and distance measuring system (the '063 system). Specifically the '063 system includes a pair of camera lenses positioned along a common baseline a predetermined distance apart and controlled by an operator to capture images of a target at different times. The camera lenses are focused on light sensitive pixel arrays that capture target images at offset positions in the line scans of the pixel arrays. A video signal processor with a computer determines the location of the offset positions and calculates the range to the target by solving the trigonometry of the triangle formed by the two camera lenses and the target.
With such a system, objects moving into the field of view of the video cameras may be monitored. Further if not only range but direction and velocity were known, objects of interest could be tracked and others ignored. To some degree, this would alleviate the problem of false alarms.